cleanup(scripts): cleanup systemd unit in DEB installer

Signed-off-by: Stanley Chan <pocketgamer5000@gmail.com>

scripts/debian/postinst.in

@@ -41,3 +41,34 @@ case "$1" in
 		fi
 	;;
 esac
+
+# Based off what debhelper dh_systemd_enable/13.3.4 would have added
+# ref: https://www.debian.org/doc/manuals/debmake-doc/ch05.en.html#debhelper
+
+if [ "$1" = "configure" ] || [ "$1" = "abort-upgrade" ] || [ "$1" = "abort-deconfigure" ] || [ "$1" = "abort-remove" ] ; then
+        # This will only remove masks created by d-s-h on package removal.
+        deb-systemd-helper unmask 'falco.service' >/dev/null || true
+
+        # was-enabled defaults to true, so new installations run enable.
+        if deb-systemd-helper --quiet was-enabled 'falco.service'; then
+                # Enables the unit on first installation, creates new
+                # symlinks on upgrades if the unit file has changed.
+                deb-systemd-helper enable 'falco.service' >/dev/null || true
+        else
+                # Update the statefile to add new symlinks (if any), which need to be
+                # cleaned up on purge. Also remove old symlinks.
+                deb-systemd-helper update-state 'falco.service' >/dev/null || true
+        fi
+fi
+
+if [ "$1" = "configure" ] || [ "$1" = "abort-upgrade" ] || [ "$1" = "abort-deconfigure" ] || [ "$1" = "abort-remove" ] ; then
+        if [ -d /run/systemd/system ]; then
+                systemctl --system daemon-reload >/dev/null || true
+                if [ -n "$2" ]; then
+                        _dh_action=restart
+                else
+                        _dh_action=start
+                fi
+                deb-systemd-invoke $_dh_action 'falco.service' >/dev/null || true
+        fi
+fi

scripts/debian/postrm.in

@@ -15,3 +15,25 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 #
+
+# Based off what debhelper dh_systemd_enable/13.3.4 would have added
+# ref: https://www.debian.org/doc/manuals/debmake-doc/ch05.en.html#debhelper
+
+set -e
+
+if [ -d /run/systemd/system ] && [ "$1" = remove ]; then
+        systemctl --system daemon-reload >/dev/null || true
+fi
+
+if [ "$1" = "remove" ]; then
+        if [ -x "/usr/bin/deb-systemd-helper" ]; then
+                deb-systemd-helper mask 'falco.service' >/dev/null || true
+        fi
+fi
+
+if [ "$1" = "purge" ]; then
+        if [ -x "/usr/bin/deb-systemd-helper" ]; then
+                deb-systemd-helper purge 'falco.service' >/dev/null || true
+                deb-systemd-helper unmask 'falco.service' >/dev/null || true
+        fi
+fi

scripts/debian/prerm.in

@@ -17,6 +17,14 @@
 #
 set -e
 
+# Based off what debhelper dh_systemd_enable/13.3.4 would have added
+# ref: https://www.debian.org/doc/manuals/debmake-doc/ch05.en.html#debhelper
+# Currently running falco service uses the driver, so stop it before driver cleanup
+
+if [ -d /run/systemd/system ] && [ "$1" = remove ]; then
+        deb-systemd-invoke stop 'falco.service' >/dev/null || true
+fi
+
 case "$1" in
 	remove|upgrade|deconfigure)
 		/usr/bin/falco-driver-loader --clean